Electrosurgical devices are used in many surgical operations. Electrosurgical devices can apply electrical energy to tissue in order to treat the tissue. An exemplary electrosurgical device can include a distally-mounted end effector having one or more electrodes. The end effector can be positioned against tissue such that electrical current is introduced into the tissue. Electrosurgical devices can be configured for bipolar and/or monopolar operation. During bipolar operation, current is introduced into and returned from the tissue by active and return electrodes, respectively, of the end effector. During monopolar operation, current is introduced into the tissue by an active (or source) electrode of the end effector and returned through a return electrode (e.g., a grounding pad) separately located on a patient's body. Heat generated by the current flow through the tissue can form hemostatic seals within the tissue and/or between tissues and thus can be particularly useful for sealing blood vessels, for example. The end effector of an electrosurgical device can also include a cutting knife that is movable relative to the tissue and the electrodes to transect the tissue.
Electrical energy applied by an electrosurgical device can be transmitted to the device by a generator. The electrical energy can be in the form of radio frequency (RF) energy. RF energy is a form of electrical energy that can be in the frequency range of about 100 kHz to about 1 MHz. During operation, an electrosurgical device can transmit low frequency RF energy through tissue, which can cause ionic agitation, friction, and/or resistive heating, thereby increasing the temperature of the tissue. Because a sharp boundary can be created between the affected tissue and the surrounding tissue, surgeons can operate with a high level of precision and control without sacrificing un-targeted adjacent tissue. The low operating temperatures of RF energy can be useful for removing, shrinking, or sculpting soft tissue while simultaneously sealing blood vessels. RF energy can work particularly well on connective tissue, which is primarily comprised of collagen and shrinks when contacted by heat.
Thermal management can be an important factor in the design and operation of electrosurgical devices. If heat is dissipated from the electrode into adjacent portions of the device too quickly, more time can be required to seal the tissue and the seal quality can be adversely affected. For example, in the case of a sealed vessel, the burst pressure of the seal can be too low if the electrode is not hot enough when the seal is formed. If heat is dissipated from the electrode into adjacent portions of the device too slowly, the electrode temperature can increase beyond an ideal range, which can undesirably cause tissue to burn and stick to the electrode. In practice, it can be difficult to regulate the transfer of heat from the electrode with high precision.
There is a continuing need for improved electrosurgical devices and related methods.